Fig. 1.

Nonreciprocal transport in a Bi₂Te₃/FeTe heterostructure. a The illustration of a Bi₂Te₃/FeTe heterostructure (Bi₂Te₃: blue, FeTe: green). The interface of Bi₂Te₃ and FeTe shows superconductivity (yellow region). The nonreciprocal transport is measured with current I along x-direction under the in-plane magnetic field B (along y-direction) perpendicular to the current. The mutual interaction between spin–momentum-locked topological surface state and superconductivity (as represented by Δ_SC) is expected at the interface as expressed in momentum space in the right circle. σ represents the spin direction of the electron. b Temperature dependence of resistance in FeTe(18 nm)/CdTe(100) (green), Bi₂Te₃(15 nm)/InP(111) (blue) and Bi₂Te₃(15 nm)/FeTe(18 nm)/CdTe(100) (red) thin films. The superconductivity and topological surface state appear at the interface between Bi₂Te₃ and FeTe as denoted by the yellow allow. c The temperature dependence of resistance in Bi₂Te₃/FeTe heterostructure under in-plane magnetic field B = 0, 2, 4, 6, 8, 10, 12, and 14 T. The resistance is measured under I = 1 μA. d The magnetic field dependence of R^2ω in Bi₂Te₃/FeTe heterostructure at T = 12 K (blue, normal state) and at T = 9.5 K (light blue, below the superconducting onset temperature) measured with a current magnitude of I = 200 μA